Female Parasitoids Research Articles

Effectiveness of Diachasmimorpha longicaudata in Killing Ceratitis capitata Larvae Infesting Commercial Fruits in Dryland Agroecosystems of Western Argentina

Ceratitis capitata (Wiedemann) (medfly) strongly affects Argentinean fruit production and export. Augmentative biological control using the exotic parasitoid Diachasmimorpha longicaudata (Ashmead) is currently applied to this problem. The ability to find and parasitize medfly larvae on a wide diversity of fruit host species is a key issue that needs to be analyzed. This research assessed the effect of the physical features of fruit on the preference of foraging D. longicaudata females and the influence of varying release density on parasitoid performance as a pest mortality factor in three fruit species. Trials were performed inside field cages under semi-arid environmental conditions in Argentina’s central-western fruit-growing region. Sweet orange, peach, and fig were tested. The fruits were inoculated with third-instar larvae of the Vienna-8 temperature-sensitive lethal medfly strain. Naïve, 5 d-old mated D. longicaudata females were released in cages at 20, 40, 80, and 160 parasitoid densities. The highest levels of medfly mortality and parasitoid emergence were recorded in fig and peach, although D. longicaudata also induced mortality in orange, a fruit with few physical features favorable to parasitism. The medfly mortality in all fruit host species significantly increased with an increased number of parasitoid females released into the field cages. Diachsmimorpha longicaudata has high potential as a medfly biocontrol agent.

Temporal variability in host availability alters the outcome of competition between two parasitoid species.

Variability in the availability of resources through time is a common attribute in trophic interactions, but its effects on the fitness of different consumer species and on interspecific competition between them are not clearly understood. To investigate this, we allowed two parasitoid species, Trichopria drosophilae and Pachycrepoideus vindemiae, to exploit Drosophila host pupae under different temporal variability treatments, either on their own or simultaneously. When tested individually (in the absence of interspecific competition), both parasitoid species had lower fitness when hosts were exposed for a short duration at high density than when exposed for a long duration at low density. When both parasitoid species exploited hosts simultaneously, interspecific competition significantly decreased the number of offspring for both parasitoid species. The outcome of this interspecific competition depended on host temporal variability, with T. drosophilae or P. vindemiae dominating in short and long host exposure treatments, respectively. These results can be explained by the combination of host availability and egg load of female adult parasitoids. When abundant hosts are provided for a short period, the ample mature eggs of the proovigenic T. drosophilae enable them to exploit hosts more efficiently than P. vindemiae, which is synovigenic. However, P. vindemiae is an intrinsically superior competitor and dominates when multiparasitism occurs. Multiparasitism is more frequent when hosts are at low levels relative to the egg load of the parasitoids. Our results clearly demonstrate that resource temporal availability can alter the outcome of competition between consumers with different reproductive traits.

High-temperature responses of Myzus persicae and its parasitoid Aphidius gifuensis in relation to heat level, duration and developmental stage.

Understanding how parasitoids respond to temperature is crucial for improving biological control strategies under the context of global warming. This study examined the suitability of Myzus persicae and its parasitoid Aphidius gifuensis to varying temperature conditions, as well as the stage-specific response of A. gifuensis to high temperatures. High temperatures had a significant impact on the both M. persicae and A. gifuensis. When exposed to 36°C, M. persicae developed more slowly and produced smaller adults compared to control, regardless of the duration of exposure (2, 4 or 6 h); additionally, the survival rate of M. persicae nymphs sharply decreased under these conditions. Exposure to 36°C for 4 h negatively impacted the development of A. gifuensis. Female parasitoids exposed to 32°C developed into smaller adults, whereas males exposed to all three temperature levels were smaller compared to control group. Female parasitoids exposed to high temperatures, regardless of the specific heat level and duration, exhibited reduced longevity and decreased fecundity. None of the parasitoids exposed to 36°C for 6 h daily developed into adults. Heat treated during early developmental stages (2 and 4 days old) had a greater influence on parasitoid development, whereas heat treatment at 4 and 6 days old had a more significant impact on its fecundity. High temperatures not only directly affected the performance of A. gifuensis, but also exerted indirect effects by influencing the quality of the host aphids M. persicae. The deleterious effects of high temperature on larvae can persist into the adult stage, affecting the longevity and reproduction of adults. These findings are important for the utilization of A. gifuensis in the control of M. persicae in warming environments. © 2024 Society of Chemical Industry.

Parasitisation activity of Spalangia cameroni and Muscidifurax zaraptor, pupal parasitoids of Musca domestica

AbstractThe house fly, Musca domestica L. (Diptera: Muscidae), is a significant pest in livestock farms and a major concern for both humans and farmed animals due to its ability to transmit over 200 pathogens. The use of pupal parasitoids is a sustainable strategy for controlling this pest. Spalangia cameroni Perkins (Hymenoptera: Spalangiidae) and Muscidifurax zaraptor Girault & Sanders (Hymenoptera: Pteromalidae) are commonly used as biocontrol agents for M. domestica. The objective of this study was to determine the oviposition peak of female parasitoids in relation to their age and the sex ratio of the adult progeny. For both species, 20 fresh M. domestica pupae (24–48 h old) were provided daily to each fertilised female for 14 days, after which the pupae were checked for parasitoid emergence. A control group of 20 pupae without female parasitoids was maintained. The results showed that S. cameroni had a higher overall percentage of parasitisation (57.7%) compared with M. zaraptor (32.4%). The parasitisation ratio of S. cameroni remained almost constant throughout the 14‐day period, whereas that of M. zaraptor decreased drastically after Day 11. Peak oviposition for S. cameroni was on Day 5 with 13 parasitised pupae per female, whereas M. zaraptor parasitised eight pupae per day on 4 days during its peak oviposition period (between Days 3 and 8). The newly emerged parasitoids had a skewed sex ratio towards females: 81% for S. cameroni and 66% for M. zaraptor. The presence of these parasitoid species resulted in fewer new house fly emergences than in the control group, where natural pupal mortality was lower in the absence of parasitoids. These findings may be useful for optimising the mass production and time‐use of the two parasitoid species for the management of house flies in livestock farms.

Proactive biological control of spotted lanternfly: Parasitism and host feeding behavior of Anastatus orientalis (Hymenoptera: Eupelmidae) on Lycorma delicatula (Hemiptera: Fulgoridae) egg masses

Lycorma delicatula (Hemiptera: Fulgoridae) is a recognized threat to perennial vine, tree crops, and forest ecosystems. Native to China, L. delicatula has invaded eastern Asian countries (The Republic of Korea [i.e., South Korea] and Japan) and is spreading rapidly through the eastern and mid-western regions of the USA. Stablished populations in these regions present a significant incursion threat to California’s multi-billion-dollar perennial crops (e.g., grape and nut production). As a part of a proactive classical biological control program targeting L. delicatula in California, USA, the egg parasitoid, Anastatus orientalis (Hymenoptera: Eupelmidae), is being evaluated for possible use against this pest should it establish in California. In support of this proactive research, the oviposition and host feeding behavior of A. orientalis was investigated. The effect of time exposure (i.e., 48-, 72-, 96-, 168-hours) on the percentage of eggs parasitized by 7-day old female parasitoids previously exposed to L. delicatula egg masses in presence/absence of a conspecific male was also investigated. Parasitism rates were significantly higher after 96 h of exposure time and offspring sex ratio did not change in any of the treatments (i.e., exposure time, presence/absence of a male). In another experiment, mated and unmated female parasitoids of three different ages (i.e., ≤ 24-, 72- and 120 h of age) were digitally video recorded for 24 h while foraging on L. delicatula egg masses and host use behaviors were quantified. Anastatus orientalis females that were 72 h old (mated) and 120 h (mated and unmated) spent significantly more time antennating and probing/ovipositing in L. delicatula egg masses than younger unmated females. An increase in host feeding behavior was always associated with increased oviposition behavior. No detrimental effects of host feeding on rates of parasitism and A. orientalis offspring emergence were detected. This finding confirms that A. orientalis is a concurrent parasitoid and can use the same host egg for feeding and parasitism. Implications of these results on possible rearing and release strategies of A. orientalis as a biological control agent of L. delicatula are discussed.

Effects of food resources on the longevity, survival, and fecundity of Paracentrobia subflava adults, an egg parasitoid of the corn leafhopper pest Dalbulus maidis

AbstractThe diet consumed by adult parasitoids can affect longevity, survival, and fecundity. Honeydew from sap‐sucking insects is an abundant food resource in the field; however, artificial diets such as commercial bee honey are often used in lab rearing. The parasitoid Paracentrobia subflava (Girault) (Hymenoptera: Trichogrammatidae) is a natural enemy of Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae). The longevity and survival of P. subflava when fed natural and artificial diets under controlled conditions have not been studied. Further, the fecundity of P. subflava when fed a diet of honey has not been investigated. Therefore, our first objective was to analyse the longevity and survival of P. subflava when fed (1) honeydew of the corn leafhopper D. maidis, (2) honey + water, (3) honey + water + pollen, (4) water, and (5) nothing (control). Our second objective was to evaluate P. subflava fecundity upon exposure to D. maidis eggs, comparing parasitoids fed with honey + water versus controls (no food or water). In the second objective, honey was chosen since it was determined during the first objective to be the optimal food. The longevity of adult parasitoids (laboratory‐reared and field‐collected) was high when fed on honey and low when fed other diets. The highest longevity was achieved with honey + water: 17 days, while the survival of adult parasitoids was only 3 days for honeydew. Interestingly, fecundity, in terms of the percentage of parasitism and the percentage of emergence, did not differ between parasitoid females that had access to honey + water as a food resource and those that had no food or water.

Does the Neotropical‐native parasitoid Ganaspis pelleranoi successfully attack the worldwide invasive pest Drosophila suzukii?

AbstractThe Asian Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a harmful invasive pest widespread throughout Argentinian fruit‐producing regions. It coexists with both pests, the sub‐Saharan African Ceratitis capitata (Wiedemann) and the Neotropical‐native Anastrepha fraterculus (Wiedemann) (both Diptera: Tephritidae), in northwestern Argentina. The Neotropical‐native parasitoid Ganaspis pelleranoi (Brèthes) (Hymenoptera: Figitidae) is frequently found in non‐crop fruit infested by those frugivorous dipterans. The northwestern Argentinian region is known for producing and exporting berries and citrus, which are affected by those pests. Thus, eco‐friendly control strategies are under assessment. This study mainly assessed the potential of the G. pelleranoi population lineage from Tucumán (GpTuc) as a D. suzukii biocontrol agent. First, both the host‐killing effectiveness and the reproductive success of GpTuc on larvae of D. suzukii, C. capitata, A. fraterculus, and Drosophila melanogaster Meigen were compared in no‐choice tests under laboratory conditions. Then, the GpTuc host preference was evaluated in dual‐choice tests (D. suzukii vs. C. capitata or A. fraterculus) under laboratory and field conditions. Naive parasitoid females were allowed to forage for 8 h on screen‐covered Petri dishes filled with host larvae under laboratory conditions and for 48 h on peaches inoculated with host larvae under field conditions. Host puparia dissections were performed to determine the number and condition of parasitoid eggs, first and second instars, such as alive/dead, without/with melanization process, and proportions of parasitized, superparasitized, and dead puparia. Drosophila suzukii was not a suitable host for the successful development of GpTuc immature stages as they did not overcome the host's immune system. However, GpTuc performed efficiently regarding D. suzukii mortality, but parasitoid specificity was restricted to both tephritid species as only thriving offspring were achieved from them. Interestingly, the effectiveness of GpTuc on D. suzukii increased when it co‐occurred with C. capitata instead of A. fraterculus, the preferred host.

Sublethal Effects of Insecticides on the Parasitism of Acerophagus flavidulus (Hymenoptera: Encyrtidae) Parasitoid of the Obscure Mealybug, Pseudococcus viburni (Hemiptera: Pseudococcidae)

Insecticides used to control agricultural pests can interfere with beneficial arthropods. This study determined the sublethal effects of two insect growth regulators—buprofezin and pyriproxyfen—and the neonicotinoid insecticide acetamiprid on adults of Acerophagus flavidulus (Brethés), a parasitoid of the obscure mealybug, Pseudococcus viburni (Signoret). A. flavidulus was exposed to insecticide residues at the minimum recommended rate of buprofezin and pyriproxyfen (1×) and 0.005× of acetamiprid on apple leaves under laboratory conditions. Each female parasitoid was in contact with the insecticide residues for 24 h and then allowed to parasitize three mealybug densities (two, four, and six nymphs) per parasitoid for 24 h. Parasitism, emergence rate, clutch size, development time, longevity, and secondary sex ratio were evaluated under each insecticide treatment and mealybug density. Application of the growth regulators buprofezin and pyriproxyfen at the labeled rate (1×) induced less sublethal effects than acetamiprid applied at a low rate (0.005×) on A. flavidulus. Pyriproxyfen and acetamiprid reduced parasitism, but they did not affect other aspects of development such as emergence rate, clutch size, development time, longevity, and secondary sex ratio. Our data suggest that buprofezin and pyriproxyfen are more compatible with A. flavidulus than acetamiprid, which could be integrated with parasitoid activity only when low residue levels in the field are attained.

Host-plant related effects on host feeding, parasitism and sex ratio of Neochrysocharis formosa (Westwood) (Hymenoptera, Eulophidae) attacking Liriomyza huidobrensis (Blanchard) (Diptera, Agromyzidae) leafminer

Liriomyza huidobrensis (Blanchard) (Agromyzidae, Diptera) was the most prevalent on crops infested with leafminers in Jordan, as it was recorded on twelve economic vegetable crops. We investigated the plant-mediated effects on the host feeding, egg laying, parasitism and adult emergence of Neochrysocharis formosa (Westwood) (Eulophidae, Hymenoptera) parasitizing L. huidobrensis larvae on seven vegetables. Results showed that the highest percentage of parasitoid feeding on L. huidobrensis larvae was on bean leaves (9.7%). The lowest percentages of parasitoid host-feeding were on the leaves of white-flowered gourd (4.5%) and eggplant (4.3%) plants. For egg laying, N. formosa females significantly preferred potato (57.7% of parasitism) and bean (46.6% of parasitism) plants. The lowest rates of parasitism occurred on eggplant (17%) and white-flowered gourd (22.3%). The full percentage of adult parasitoid emergence was in bean and broad bean. All plant hosts showed a significant superiority in the parasitoids emergence over eggplant (92.9%) and tomato (85.7%). The highest percentages of emerged parasitoid females were on potato (75%) and the lowest percentage was on eggplant (52%).

Trichopria anastrephae as a Biological Control Agent of Drosophila suzukii in Strawberries.

In South America, the resident pupal parasitoid Trichopria anastrephae Costa Lima (Hymenoptera: Diapriidae) is a potential biological control agent of the pest Drosophila suzukii Matsumura (Diptera: Drosophilidae). In the present study, we (1) examined the behavior of T. anastrephae towards different host (D. suzukii) and host-substrate (strawberry) cues in choice and non-choice bioassays in laboratory, and (2) examined the density-dependent parasitism of T. anastrephae in D. suzukii-infested strawberries in a greenhouse. When given a choice, female parasitoids walked longer over chambers with fruits infested with eggs, larvae, or pupae of D. suzukii, when compared to healthy uninfested strawberries, and over overripe fruits when compared to unripe or ripe fruits. In the greenhouse assay, we observed an increase in parasitism and a decrease in the number of D. suzukii emerging per fruit with an increase in the number of parasitoids released. Our results allow a better understanding of the behavior and parasitism of T. anastrephae in D. suzukii-infested strawberries and provide useful data for potential biological control programs using this parasitoid.

Oviposition behavior of the quasi-gregarious parasitoid, Ooencyrtus kuvanae (Hymenoptera: Encyrtidae).

The parasitoid wasp, Ooencyrtus kuvanae (Howard) (Hymenoptera: Encyrtidae), is a natural enemy of the spongy moth, a significant forest pest in North America. We investigated the oviposition behavior of O. kuvanae females on spongy moth egg masses by (i) presenting female parasitoids with a single spongy moth egg mass that was replaced every day, 2nd day, 4th day, 8th day, or 16th day (which is the total length of the oviposition period) and (ii) presenting female parasitoids with 1, 2, 4, or 8 egg masses at a time. Offspring developmental length ranged from 18 to 24 days. On average, male offspring exhibited faster developmental times, emerging approximately 1 day ahead of females. The amount of time that adult females spent on an egg mass affected the number of parasitized eggs. Specifically, more offspring emerged in the 4-, 8-, and 16-day treatments than in scenarios involving daily or every second-day egg mass replacement. The percentage of male offspring decreased as the number of egg masses presented to females increased. Interestingly, the total number of female offspring remained constant, but the number of male offspring decreased with an increase in the number of egg masses and time spent by the parent within a patch. The observed sexual dimorphism in development time, the influence of resource availability on offspring sex ratios, and flexible oviposition patterns illustrate the adaptability of O. kuvanae in response to varying conditions. These insights have implications for our understanding of parasitoid-host interactions and their potential role in biological control strategies.

Keeping a close eye on the searching behaviour of the mass-reared parasitoid Dichasmimorpha longicaudata: addressing a standardised test

ABSTRACT Tephritid fruit flies are responsible for many losses in the fruit market due to direct damage to fruits and their quarantine restrictions. Augmentative parasitoid releases are an effective method of biological control that is complementary to the sterile insect technique (SIT) currently used for the management of many tephritid species. However, mass-produced parasitoids must exhibit high-quality attributes that are crucial for the reduction of pest populations. Females must be able to disperse and locate host larvae following kairomones. Nevertheless, there is currently no standardised, fast-processing method to assess the quality of searching parasitoids. Since parasitoid effectiveness is linked to flight ability, we developed a test with a larval-odour device that aimed to measure the quality of female parasitoids via their ability to locate host larvae by their odour. As an odour source, we applied a used or clean artificial host diet on a 3 × 2 cm piece of filter paper. We diluted the diets in ethanol at 1/1, 1/2, 1/3, and 1/4 (% mass/vol) to obtain an odour gradient. Female wasps landed and attempted to oviposit more frequently on devices treated with used diet than on those treated with clean diet. We suggest that this test can be implemented as a simple and fast method to evaluate the searching behaviour of mass-reared parasitoids of fruit fly larvae.

Age- and Density-Dependent Parasitism Rate and Development Time of the Generalist Egg-Parasitoid Ooencyrtus telenomicida (Hymenoptera: Encyrtidae) on Eggs of the Brown Marmorated Stink Bug, Halyomorpha halys.

Halyomorpha halys (Hemiptera: Pentatomidae) is an invasive pest species that was imported into Greece in 2011 and since then, has caused severe qualitative and quantitative damage to economically important crops. Its management relies mainly on the use of broad-spectrum insecticides, with little to no information available concerning the potential use of native parasitoids in terms of classical biological control. Our study aimed to assess the parasitism rate and development time of the gregarious egg parasitoid Ooencyrtus telenomicida (Hymenoptera: Encyrtidae) on H. halys egg-masses, depending on several factors such as: (i) age of parasitoids, (ii) density of parasitoids, (iii) age of host eggs, and (iv) oviposition experience of parasitoids. According to our results, the younger the host eggs and the more parasitoids, the higher the parasitism rate achieved by adults of O. telenomicida, with the maximum mean value of the parasitism rate observed with 1-day-old host eggs and 4 parasitoid pairs (57.3%). On the contrary, the lowest mean value of the parasitism rate was observed with 4-day-old host eggs and 1 parasitoid pair (6.5%). Similarly, the age of parasitoids significantly affected parasitisation. The older the parasitoids were, the higher the parasitism rate achieved by adults of O. telenomicida, with a three-fold higher parasitism rate observed at 3-4 and 5-6-day-old O. telenomicida, compared to 1-2-day-old (31.8, 32.4, and 12.1%, respectively). Individuals that developed in younger host eggs displayed a shorter development time, and the shortest development time was observed for O. telenomicida laid by 2 parasitoid pairs. Parasitoid age did not affect the development time of O. telenomicida, although there was a tendency for individuals laid by younger female parasitoids to exhibit a shorter development time. Our findings provide valuable information on the potential use of O. telenomicida as a biocontrol agent of H. halys.

Low concentrations of selenium nanoparticles enhance the performance of a generalist parasitoid and its host, with no net effect on host suppression.

The environmental and economic costs of conventional insecticides have stirred an interest in alternative management tactics, including the use of nanotechnologies. Selenium nanoparticles (SeNPs) have many applications in agriculture but may not be compatible with biological control; however, low concentrations of SeNPs may benefit natural enemies via hormesis. This study investigates the concentration-dependent effects of SeNPs (0-1000 mg L-1 ) on Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae), a generalist parasitoid of stored product pests. The LC50 of SeNPs was 1540 mg L-1 for female parasitoids and 1164 mg L-1 for males. SeNPs had a significant hormetic effect; average lifespan increased by 10% at a concentration of 4.03 mg L-1 for females and by 35% at 13.83 mg L-1 for males. In a bioassay including hosts [the azuki bean beetle, Callosobruchus chinensis (L.) (Coleoptera: Chrysomelidae: Bruchinae)], a low concentration of SeNPs (25 mg L-1 ) enhanced the performance of female parasitoids; lifespan increased by 23% and the number of offspring increased by 88%. However, the number of emerging hosts did not significantly decrease; in the absence of parasitism, SeNPs actually improved host emergence by 17%. Because higher concentrations of SeNPs reduced parasitoid lifespan, whereas low concentrations enhanced not only parasitoid performance but also host emergence, practitioners should exercise caution when considering SeNPs for use in integrated pest management. © 2023 Society of Chemical Industry.

Isofemale line as an alternative to maintain quality of Telenomus remus Nixon, a biological-control agent for fall armyworm

This study evaluated whether rearing a regular line and an isofemale line of Telenomus remus Nixon for successive generations in laboratory conditions changed its flight capacity, parasitism, and longevity, desirable characteristics for a biological-control agent. The regular line of T. remus was re-introduced to laboratory rearing conditions from the field. The isofemale line was selected through inbreeding for nine generations, reducing its genetic variability. Flight capacity, parasitism, and longevity were evaluated over 11 generations in the regular strain, adding more two evaluations of parasitism and longevity (F17 and F19) and 20 generations in the isofemale line. Flight capacity was evaluated in flight-test units. Parasitism and lifespan were evaluated by offering egg-masses of S. frugiperda daily to individual females and counting the number of parasitized eggs, until the wasps died. The regular line of T. remus was affected by laboratory rearing over time. The proportion of flying individuals decreased by around 20 % between generations F1 and F6; the parasitism capacity was similar across generations; and longevity was similar in F1 and F6 (around 12 days), differing from F11 (8 days). Parasitism did not differ significantly in the T. remus isofemale line in the three generations evaluated, with no large variations in the parasitism potential in recently emerged female in any generation. The longevity of the parasitoid females was similar in generations F1 and F20 (7.3 and 8.1 days respectively) but differed from the F10 generation (15.2 days). Laboratory rearing of the regular line of T. remus over successive generations changed its flight capacity, parasitism, and longevity. Use of a T. remus isofemale line may be an alternative to maintain flight capacity and parasitism of this S. frugiperda biological-control agent over generations.

Can the use of particle films for fruit protection against medfly alter the behavior of the parasitoid Diachasmimorpha longicaudata?

AbstractThe use of particle films, especially kaolin‐based films, is a promising technology to control infestations of Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), an important pest of fruits. However, its effects on one of the most important biocontrol agents of this fly in Brazil, the parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae), are unknown. This study aimed to evaluate the influence of mineral particle films on the oviposition behavior of D. longicaudata and to determine the success of parasitism in C. capitata using grape (Vitis vinifera L., Vitaceae) as substrate. Before the bioassays, the color characteristics, firmness, total soluble solid content, pH, and titratable acidity of the fruits were determined. Grapes were immersed in suspensions of kaolin Surround WP, kaolin 607, kaolin 608, and distilled water (control); thereafter, they were perforated, and two C. capitata third instars were inserted into the orifice. The grapes were then exposed to a female parasitoid. The frequency and duration of the following behavioral parameters of D. longicaudata were evaluated: landing on fruit, inspection, buccal contact, oviposition, cleaning, resting on fruit, and resting on cage. Furthermore, parasitism success was assessed. Mineral particle films altered the color and firmness of the grapes. The females of D. longicaudata performed all distinguished behaviors in treated and untreated grapes, except buccal contact, which was not done on the kaolin‐treated fruits. Kaolin 607 negatively affected landing, inspection, puncture, and rest behaviors; kaolin Surround WP only reduced inspection and puncture. Fruit coating with all three tested kaolin products decreased the success of parasitism of D. longicaudata, indicating that particle films applied to plant organs can affect the behavior of this natural enemy.

Topical and field‐tested residual effects of globally used insecticides on the parasitoid Tamarixia radiata released against the Asian citrus psyllid, Diaphorina citri

AbstractTamarixia radiata (Waterston) (Hymenoptera: Eulophidae) is the key parasitoid of the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), in several citrus‐producing regions of the world. Chemical control is common to suppress ACP. Insecticides from globally used classes of insecticides for controlling ACP were tested on its primary parasitoid, T. radiata. Evaluations included dose–response of dimethoate, fenpropathrin, and imidacloprid in a topical application and lethal and sublethal effects from residues of imidacloprid, fenpropathrin, horticultural mineral oil (HMO), pyrethrin, and spirotetramat at 1, 3, and 7 days after application (DAA) of sprays on citrus trees in the orchard. The parasitism potential of the females that survived insecticide exposure was evaluated on untreated nymphs of ACP developing on citrus shoots and untreated parasitoid females were evaluated on nymphs treated with insecticides. In the topical application, imidacloprid was 8× more toxic to T. radiata than dimethoate and fenpropathrin. The lethal effect of the residues from imidacloprid and fenpropathrin sprays was more detrimental than other insecticides. Parasitoid mortality from 1‐ to 3‐day‐old residues averaged 90–96% for imidacloprid, 83–94% for fenpropathrin, 38–77% for pyrethrin, 43–44% for HMO, and 17–33% for spirotetramat. Parasitism by females that survived insecticide exposure was reduced by 71–88% from fenpropathrin, 28–59% from pyrethrin, 31–55% from imidacloprid, 44–4% from spirotetramat, and 39–11% from HMO compared to untreated females. The lethal and sublethal effects of all insecticides on T. radiata were significantly reduced at 7 DAA, suggesting a lower impact on its establishment and performance if releases are made after a week from spray application.

Oviposition fluids from adult wasps mediate interspecific competition between parasitoid larvae

Abstract Parasitoid wasp larvae engage in intense interspecific competition when sharing a host insect, with lethal consequences for the losers. Larval parasitoid competition is generally thought to be resolved by physical traits, such as enlarged mandibles. Although solitary parasitoid larvae are typically superior competitors against gregarious larvae, such physical traits are unlikely to be effective against large numbers of competitors. Larval competition may instead be mediated by maternal factors that increase the survival of offspring facing interspecific competition, thus increasing parental fitness. When laying eggs inside a host, many female parasitoids also inject oviposition fluids that are known to suppress host immune responses, permitting successful offspring development. We explored whether the oviposition fluids of two wasp species in the genus Cotesia (Cotesia rubecula, a strong competitor that almost always wins interspecific competition against a weaker competitor, Cotesia glomerata) might also represent maternal factors that improve the interspecific competitive ability of their offspring. We demonstrate that injections of both venom and calyx fluid from C. rubecula can inhibit egg hatching and larval development of C. glomerata. Venom from C. rubecula decreased C. glomerata egg development by 2.7 times, and calyx fluid injections caused deformities in 23% of developing C. glomerata. In contrast, reciprocal injections of the oviposition fluids from C. glomerata did not inhibit the development of C. rubecula. Our results show that maternal factors can improve the interspecific competitive ability of parasitoid larvae, challenging the previous assumptions that larval competition was resolved primarily through physical combat or larval secretions.

Interactions between egg parasitoids and predatory ants for the biocontrol of the invasive brown marmorated stink bug Halyomorpha halys

AbstractThe brown marmorated stink bug Halyomorpha halys is an Asian species that has become a major agricultural pest in North America and Europe. Ants from the genus Crematogaster are predators of H. halys nymphs in Asia, as well as in the Mediterranean, where known native predators are still few. At the same time, ants usually do not harm H. halys eggs, which are the target of the main biological control agents, the scelionid parasitoids of the genus Trissolcus. However, ants, as generalist predators and territorial organisms, may kill or displace a variety of other insects, potentially interfering with parasitoids and biological control programmes. We conducted laboratory experiments to investigate the interactions between the Mediterranean ant Crematogaster scutellaris and the parasitoids T. japonicus and T. mitsukurii, evaluating the possibility that the ants could damage the parasitized eggs, attack the parasitoids during emergence or interfere with the egg‐laying behaviour of female parasitoids. Our results demonstrate that C. scutellaris is not able to damage parasitized eggs and is not aggressive towards adult parasitoids at any stage. The presence of ants can slow down the parasitization rate in T. mitsukurii females in the smallest laboratory setups; however, this has not been observed in a more natural setting. We suggest that ants may play a complementary role together with egg‐parasitoids in the control of H. halys without interfering with each other.

Preference study of Trichogramma pintoi (Voegele) (Hymenoptera:Trichogrammatidae) on host eggs of different ages and species

Eggs of Ephestia kuehniella (Zeller), Cadra cautella (Walker) and Plodia interpunctella (Hübner) are host of parasitoid Trichogramma pintoi (Hymenoptera: Trichogrammatidae) which is used in biological control of pests. In this study, the host species and egg age preferences were determined in the parasitization performance of the adult female of T. pinto. For host species and egg age preference, 1, 2, 3 and 4 days old eggs from three different hosts were given to the parasitoid which were kept in controlled conditions until they hatched and then counted. Adult T. pintoi species were also stored at 4±1 °C up to 4 days. It was determined that the fecundity and life span of female parasitoids decreased as the storage period increased. T. pintoi was found to prefer up to 1 day eggs old in all three hosts. Parasitoid preferred 2, 3, and 4 days old eggs of all host species at the similar rates. Eggs of E. kuehniella and C. cautella were determined as the most preferred host, followed by eggs of P. interpunctella. Adult T. pintoi females stored for 1 day were found as the most surviving female individuals. The highest parasitization rate was also determined in females stored for 1 day. Host species, egg age preference and storage time of adult parasitoid are thought to be very important in mass production and release studies of T. pintoi.